This invention relates generally to cartridges for automatic arms, and specifically .41 caliber cartridges.
It is well known that there are existing industry's standards for the external dimension of cartridges used in fire arms. For reliable service in arms and the like, the outside diameter of a cartridge, projectile diameter, flash hole dimension, primer pocket, must all be with in prescribed limits to assure utilization of a particular cartridge in a specific gun. For 0.41 caliber cartridges, the inner diameter of the upper portion of a cartridge should be .41 inches, and the overall length of the cartridge approximates 0.9 inches. Thus, the contour of the cartridge body is the only area where the performance of the bullet can be altered, thereby altering projectile velocity, within limits prescribed by the strength of the shell casing and the associated charge of powder contained therewithin.
The following patents reflect the state of the art of which applicant is aware in so far as these patents appear to be germane to the patent process.
U.S. Pat. No. 2,402,068 Meador PA1 U.S. Pat. No. 2,831,287 Maillard PA1 U.S. Pat. No. 3,830,157 Donnard et al. PA1 U.S. Pat. No. 3,998,161 Booth
Of these, the patent to Meador is of great interest since he teaches the use of ammunition having specific contours which effect the overall capabilities of the cartridge. FIG. 2 for example is directed to a cylindrical case blank prior to being tapered and necked in the appropriate fashion as suggested in FIG. 3, in which the inventor appreciates the need for walls of various thickness contingent upon the load imposed thereon. However, this device is suitably configured for cartridges made of steel and not brass as in the instant application, and therefore the contour and appropriate angulations reflect not only this difference but the fact that the forces generated in the Meador invention is designed for higher internal pressure, up to 50,000 psi in which 1,000 rounds per minute or more are fired. By way of contrast, forces according to the instant application very rarely exceed 35,000 psi and the cartridge according to the instant application is made of brass requiring different configurations. More specifically, the radius of curvature in the Meador patent is constant, and in the instant application the radius of curvature changes in an elliptical fashion with other variations in wall thicknesses for advantages to be set forth hereinafter.
Donnard teaches the use of a plastic lining in combination with an aluminium casing to minimize the amount of erosive damage when hot gases escape.
Booth teaches the use of a cartridge adapter for use with revolvers in which an exterior bottle neck case involving a separate cylindrical sleeve is suitably fashioned so that a revolver that has a larger bullet chamber could thusly use a greater charge. This reference does not touch upon the internal casing geometries for the associated benefits according to the instant application.
Maillard teaches the use of a multi-pieced casing as opposed to the instant application in which the internal geometry of the casing is not the primary interest, rather the stepped portions used to crimp a bullet in the cartridge opening and the associated contours therewith are the focal point of that invention.
By way of contrast, the instant application is directed to and teaches an instrumentality for increasing the projectile velocity while not exposing the cartridge to an increased likelihood of unwanted expansion, cracking, or distortion by providing a contour and thickened areas of the casing within certain specified limits so as to provide an improved cartridge over the prior art, the contour being specifically formulated with a .41 caliber ammunition in mind. The elliptical configuration at the head end of the cartridge body involved in this instant application utilizes the axiom of the parabolic curve to direct discharged gas forces more generally against the mouth of the cartridge case, essentially in a line that is parallel to the centerline of the cartridge body from the flash hole to the cartridge mouth.